1. Field of Invention
The present invention relates to a multiple chambered semiconductor wafer processing system and, more particularly, an apparatus containing two or more buffer chambers containing robots for transporting wafers to and from semiconductor wafer processing equipment.
2. Background of Prior Art
Semiconductor wafer processing is performed by subjecting a wafer to a plurality of sequential processes. These processes are performed in a plurality of process chambers. An assemblage of process chambers served by a wafer transport robot is known as a multi-chamber semiconductor wafer processing tool or cluster tool.
Previous cluster tools consisted of a single buffer chamber which housed a wafer transport robot that distributed wafers and managed a plurality of processing chambers. FIG. 1 depicts a schematic diagram illustrative of a multiple process chamber, single buffer chamber semiconductor wafer processing tool known as the Centura(copyright) Platform manufactured by Applied Materials, Inc. of Santa Clara, Calif. FIG. 2 depicts a schematic diagram illustrative of a multiple process chamber, single buffer chamber semiconductor wafer processing tool having a xe2x80x9cdaisy-chainedxe2x80x9d preparation chamber known as the Endura(copyright) Platform manufactured by Applied Materials, Inc. of Santa Clara, Calif. Both Centura(copyright) and Endura(copyright) are trademarks of Applied Materials, Inc. of Santa Clara, Calif. These tools can be adapted to utilize either single, dual or multiple blade robots to transfer wafers from chamber to chamber.
The cluster tool 100 depicted in FIG. 1 contains, for example, a plurality of process chambers, 104, 106, 108, 110, a buffer chamber 124, and a pair of load lock chambers 116 and 118. To effectuate transport of a wafer amongst the chambers, the buffer chamber 124 contains a robotic transport mechanism 102. The transport mechanism 102 shown has a pair of wafer transport blades 112 and 114 attached to the distal ends of a pair of extendible arms 113a, 113b, 115a and 115b, respectively. The blades 112 and 114 are used for carrying individual wafers to and from the process chambers. In operation, one of the wafer transport blades (e.g. blade 112) of the transport mechanism 102 retrieves a wafer 122 from a cassette 120 in one of the load lock chambers (e.g. 116) and carries that wafer to a first stage of processing, for example, physical vapor deposition (PVD) in chamber 104. If the chamber is occupied, the robot waits until the processing is complete and then swaps wafers, i.e., removes the processed wafer from the chamber with one blade (e.g., blade 114) and inserts a new wafer with a second blade (e.g., blade 112). Once the wafer is processed (i.e., PVD of material upon the wafer, the wafer can then be moved to a second stage of processing, and so on. For each move, the transport mechanism 102 generally has one blade carrying a wafer and one blade empty to execute a wafer swap. The transport mechanism 102 waits at each chamber until a swap can be accomplished.
Once processing is complete within the process chambers, the transport mechanism 102 moves the wafer 122 from the last process chamber and transports the wafer 122 to a cassette 120 within the load lock chamber 118.
The cluster tool 200 with daisy-chained wafer preparation chamber 204 depicted in FIG. 2 contains, for example, four process chambers 250, 252, 254, 256, a buffer chamber 258, a preclean chamber 210, a cooldown chamber 212, a prep chamber 204, a wafer-orienter/degas chamber 202, and a pair of load lock chambers 260 and 262. The prep chamber 204 is centrally located with respect to the load lock chambers 260 and 262, the wafer orienter/degas chamber 202, the preclean chamber 210, and the cooldown chamber 212. To effectuate wafer transfer amongst these chambers, the prep chamber 204 contains a prep robotic transfer mechanism 206, e.g., a single blade robot (SBR). The wafers 122 are typically carried from storage to the tool 200 in a cassette 120 that is placed within one of the load lock chambers 260 or 262. The SBR 206 transports the wafers 122, one at a time, from the cassette 120 to any of the three chambers 202, 210 or 212. Typically, a given wafer is first placed in the wafer orienter/degas chamber 202, then moved to the preclean chamber 210. The cooldown chamber 212 is generally not used until after the wafer is processed within the process chambers 250, 252, 254 and 256. Individual wafers are carried upon a prep wafer transport blade 208 that is located at a distal ends of a pair of extendible arms 264a and 264b of the SBR 206. The transport operation is controlled by a sequencer (not shown).
The buffer chamber 258 is surrounded by, and has access to, the four process chambers 250, 252, 254 and 256, as well as the preclean chamber 210 and the cooldown chamber 212. To effectuate transport of a wafer amongst the chambers, the buffer chamber 258 contains a second transport mechanism 214, e.g., a dual blade robot (DBR). The DBR 214 has a pair of wafer transport blades 112 and 114 attached to the distal ends of a pair of extendible arms 266a, 266b and 268a, 268b, respectively. In operation, one of the wafer transport blades (e.g., blade 114) of the DBR 214 retrieves a wafer 122 from the preclean chamber 210 and carries that wafer to a first stage of processing, for example, physical vapor deposition (PVD) in chamber 250. If the chamber is occupied, the robot waits until the processing is complete and then swaps wafers, i.e., removes the processed wafer from the chamber with one blade (e.g., blade 114) and inserts a new wafer with a second blade (e.g., blade 112). Once the wafer is processed (i.e., PVD of material upon the wafer), the wafer can then be moved to a second stage of processing, and so on. For each move, the DBR 214 generally has one blade carrying a wafer and one blade empty to execute a wafer swap. The DBR 214 waits at each chamber until a swap can be accomplished.
Once processing is complete within the process chambers, the transport mechanism 214 moves the wafer from the process chamber and transports the wafer 122 to the cooldown chamber 212. The wafer is then removed from the cooldown chamber using the prep transport mechanism 206 within the prep chamber 204. Lastly, the wafer is placed in the cassette 120 within one of the load lock chambers, 260 or 262.
Although the prior art has shown itself to be a dependable tool for processing semiconductor wafers, a number of design shortcomings are apparent. One example is the limited number of process chambers which can be serviced by the wafer transfer mechanism. Although the size of the buffer chamber can be increased to house a mechanism with a greater range of motion thus allowing for an increase in the number of processing chambers, this solution is not favored since the foot-print (or consumed floor space) of the cluster tool would become prohibitively large. A minimal tool foot-print is an important design criteria.
A second example of the shortcomings in the prior art is the lack of serviceability of the buffer chamber. As depicted in both FIGS. 1 and 2, the buffer chamber is surrounded by processing chambers and other chambers. When either the wafer transfer mechanism or other components located within the buffer chamber requires service, access is extremely limited. As such, the removal of one of the surrounding chambers is required to gain access to the buffer chamber. This causes an extended period of time to be expended for service, while increasing the probability of component wear and damage due to the removal and handling of the above mentioned components.
Another example of the shortcomings in the prior art is the inability to cluster buffer chambers for use in serial wafer processing. Serial processing often requires more processing chambers than are available on a cluster tools found in the prior art. When additional processing is required, the wafer must be removed, transported and inserted from one cluster tool to a second cluster tool. This interruption and removal of the wafer from a tool""s controlled environment results in additional time required to complete wafer processing and an increase in the probability of damage or contamination of the wafer.
As illustrated above, a need exists in the art for a multiple process chamber semiconductor wafer processing tool which allows for an increased number of processing chambers while minimizing tool foot-print, increasing wafer processing throughput, and consolidating peripheral components while allowing access for service and maintenance.
The disadvantages heretofore associated with the prior art are overcome by an invention of a method and apparatus for transporting wafers to and from wafer processing chambers utilizing a dual buffer chamber within a multiple process chamber semiconductor wafer processing system or cluster tool. The invention provides for additional number of processing chambers in the cluster tool without compromising system foot-print. The invention also provides increased throughput, accessibility to the buffer chamber and the ability to cluster buffer chambers to facilitate serial wafer processing.
One embodiment of the invention contains at least one polygonal structure having a plurality of sides and at least one of said sides having at least two process chambers disposed thereupon. The process chambers define an access area to said polygonal structure. Further, the polygonal structure has a first buffer chamber, a second buffer chamber and at least one wafer transfer location disposed within said polygonal structure. The first and second buffer chambers further have a first and a second lid disposed thereabove, respectively, thereby defining single environment within said first and second buffer chambers. Additionally, the first and second buffer chambers may contain a plurality of slit valves disposed about and selectively isolating said first and second buffer chamber, thereby defining a first and second environment within said first and second buffer chambers, respectively.
A second embodiment of the invention comprises a first polygonal module having a plurality of sides, at least a second polygonal module having a plurality of sides, and at least one mating chamber for connecting said first and said at least second polygonal modules. The first and at least second polygonal modules each further comprise a first and a second process chamber disposed on at least one of their sides that define an access area. Additionally, the apparatus contains at least one wafer transfer location and at least one buffer chamber disposed within said first polygonal module and preferably a first buffer chamber and a second buffer chamber. Said first and second buffer chambers further comprise a plurality of slit valves creating a first and a second environment within said first and said second buffer chamber, respectfully. The advantage of this configuration utilizing multiple buffer chambers is that the wafer may be transported from one modular buffer chamber to a second modular dual buffer chamber without the wafer leaving the controlled environment created within the cluster tool. This allows for expedited serial processing of wafers while minimizing wafer damage and contamination. Specifically, two or more modular buffer chambers may be daisy chained together through the use of a mating chamber to form the modular dual buffer chamber.
In a third embodiment of the invention, a semiconductor workpiece processing apparatus comprises at least one polygonal structure having a plurality of sides; a buffer chamber disposed within said at least one polygonal structure; a lid disposed above said at least one polygonal structure thereby defining a single environment within said buffer chamber; and at least two wafer transfer mechanisms disposed within said buffer chamber. The lack of a center wall allows for a reduction in tool""s foot-print. If the demands on foot-print size outweigh the need for ease of access to the buffer chamber, the access area may be reduced or eliminated to further minimize the foot-print area. This embodiment allows for faster wafer processing and greater throughput since the time required to open and close slit valves, and match environments is eliminated. The apparatus further comprises at least six slit valves disposed within said buffer chamber and a first and second process chamber disposed on one of said sides defining an access area between said first and second process chamber and said one side.